This project will examine how neuronal ensembles within the hippocampus, as well as associated[unreadable] parahippocampal cortical areas and prefrontal cortex, represent information in the service of episodic[unreadable] memory for non-spatial information. Our experiments are guided by the hypothesis that information about[unreadable] individual items and spatial context are separately represented in distinct parahippocampal areas, that area[unreadable] CAS encodes items in the context in which they were experienced, and that area CA1 encodes and retrieves[unreadable] the order in which the items were experienced; and our experiments are guided by Hasselmo's models of the[unreadable] mechanisms underlying this scheme. Multi-channel microelectrodes will be used to record the firing patterns[unreadable] of neurons in hippocampal, parahippocampal, and prefrontal areas in rats performing hippocampaldependent[unreadable] tasks that assess rats' ability to remember once-presented sequences of odors and to[unreadable] disambiguate overlapping odor sequences. In the sequence memory paradigm, we will characterize and[unreadable] localize sequence coding, spatial context coding, and coding of item familiarity within this brain system. In[unreadable] the sequence disambiguation paradigm, we will test the hypothesis that overlapping events in two[unreadable] sequences are represented distinctly for each sequence. In both paradigms, we will determine whether[unreadable] there are specific phases of the theta rhythm on which encoding and retrieval of sequence information occur,[unreadable] and whether sequential information from recent experiences persists during a memory delay. For all of[unreadable] these measures we will characterize the extent to which neural firing patterns predict memory performance.[unreadable] The design and focus of these studies is guided by observations of humans performing[unreadable] similar tasks and provides a cellular level analysis not possible in functional imaging studies on humans.[unreadable] These experiments proposed here will be compared with parallel studies on spatial sequence processing, seeking to identify common fundamental mechanisms of non-spatial and spatial sequence[unreadable] representation. The experiments are aimed to test models and to guide the further development[unreadable] of models of hippocampal circuitry that support the temporal organization of episodic memory.